The present invention relates generally to medical devices and methods including catheters, systems and methods for maintaining effective retrograde perfusion to the cerebral circulation during global or focal cerebral ischemia.
Patients experiencing cerebral ischemia often suffer from disabilities ranging from transient neurological deficit to irreversible damage (stroke) or death. Cerebral ischemia, i.e., reduction or cessation of blood flow to the central nervous system, can be characterized as either global or focal. Global cerebral ischemia refers to reduction of blood flow within the cerebral vasculature resulting from systemic circulatory failure caused by, e.g., shock, cardiac failure, or cardiac arrest. By contrast, focal cerebral ischemia refers to reduction of blood flow to a specific area(s) of the brain. Shock is the state in which failure of the circulatory system to maintain adequate cellular perfusion results in reduction of oxygen and nutrients to tissues. Typically within minutes of circulatory failure, tissues become ischemic, particularly in the brain.
In both global and focal ischemia, patients develop neurologic deficits due to the reduction in cerebral blood flow. Treatments should include measures to increase blood flow to the cerebral vasculature to maintain viability of neural tissue, thereby increasing the length of time available for interventional treatment and minimizing neurologic deficit while waiting for resolution of the ischemia. Augmenting blood flow to the cerebral vasculature is not only useful in treating cerebral ischemia, but may also be useful during interventional procedures, such as carotid angioplasty, stenting, percutaneous valve replacement, or endarterectomy, which might otherwise result in focal cerebral ischemia.
Anoxic brain injury results in permanent neural tissue death after only as little as five minutes in normothermic conditions. Such conditions can occur during a multitude of clinical settings such as either embolic or ischemic cerebrovascular accidents; intraoperative, septic or hemorrhagic hypotension and shock; as well as during cardiac, aortic, vascular and intracranial surgery. These conditions represent one of the leading causes of deaths in the population and currently define brain death.
During the last three decades, physicians and scientists from different specialties have been interested and involved in the research of cerebral protection. Their focus has been as diverse as their suggested solutions.
Vascular surgeons have focused on the delivery side of the equation by employing blood thinning agents such as aspirin and heparin. They have also utilized numerous intracarotid shunt devices to enhance cerebral protection during carotid endarterectomy surgery by maintaining antegrade perfusion.
Neurologists and neurosurgeons have focused mostly on the demand side of the equation by utilizing pharmacologic agents such as Phenobarbital that decrease the metabolic demands of the brain. They have occasionally also used some intraoperative hypothermia.
The most significant contribution to cerebral protection has however been made by cardiovascular surgeons and researchers since they have focused on both the delivery and the demand sides of the overall equation. Their long standing work with cold cardioplegia solutions, severe hypothermia and circulatory arrest during cardiac and aortic surgery have led the way to appreciating the importance of hypothermia and the use of cold retrograde blood perfusion through the venous system in providing significant cerebral protection. Furthermore, it was noted that during circulatory arrest performed for the resection of ascending aortic aneurysms, to protect the brain with both systemic hypothermia and also retrograde cold blood perfusion through the superior vena cava (SVC), part of that cold venous blood was being diverted to both upper extremities through the subclavian veins.
It was therefore suggested to apply bilateral blood pressure cuffs to both arms during the circulatory arrest and inflating them to eighty to a hundred millimeters of mercury. This would result in most of the cold blood being diverted to the brain resulting in better perfusion and better cooling of the brain during circulatory arrest and translating into better cerebral protection.
This concept was observed clinically on a series of patients. Their circulatory arrest temperatures ranged from 25 to 27 degrees Celsius instead of the normal 16 to 18 degrees Celsius, a full ten degrees warmer. Higher temperatures were tolerated mainly due to the better perfusion of cold blood to the brain, thus alleviating the need for even colder blood. This, of course, resulted in less time to cool the body temperature down and less time to resuscitate the patient and significantly less complication rates overall. Their circulatory arrest period ranged from twenty-nine to sixty-seven minutes. There was universal cerebral protection with no neurologic deficits. The retrograde cold blood perfused also had a temperature of 25 to 27 degrees Celsius. This concept of cerebral protection has been extended to the fields of medical and surgical treatment of cerebrovascular accidents whether due to embolic, ischemic or hemorrhagic (cerebral aneurysms and arteriovenous malformations) events.
According to the present invention, methods, systems and devices are provided for perfusing a brain territory, retrogradely, which is ischemic, through its venous drainage system.
According to one embodiment, a method is provided to maintain or increase cerebral perfusion during global cerebral ischemia, for example. The method perfuses an oxygenated medium, e.g., blood, in the cerebral vasculature of a patient. For example, increased cerebral perfusion or blood flow retrogradely is provided during global cerebral ischemia. The method includes: (1) positioning left and right pressure cuffs on the respective left and right upper extremities of a patient; (2) providing a catheter having a multi-configuration, the catheter having a proximal region, a distal region, and an expandable member, e.g., a balloon, which is circumferentially disposed and sealably attached about the catheter and mounted substantially adjacent or near the distal end of the catheter; (3) inserting the catheter into a subclavian vein of the patient; alternatively, the catheter may be introduced through the femoral vein, also in a conventional manner; (4) advancing the catheter through the (right or left) subclavian (or right or left femoral vein) such that the expandable member is positioned to occlude the superior vena cava substantially proximal to the take-off of the left innominate vein of the patient.
According to another preferred embodiment a method is provided to maintain or increase cerebral perfusion during focal ischemia, for example the method perfuses an oxygenated medium e.g., blood, in the cerebral vasculature of a patient. For example increased cerebral perfusion of blood or blood flow retrogradely is provided during focal cerebral ischemia. The method includes: (1) providing a catheter having a multi-configuration, the catheter having a proximal region, a distal region, and an expandable member, e.g., a balloon, which is circumferentially disposed and sealably attached about the catheter and mounted substantially adjacent or near the distal end of the catheter, (2) inserting the catheter into a subclavian, femoral or jugular vein in a conventional manner, (3) advancing the catheter such that the expandable member is positioned to occlude the internal jugular vein on the side ipsilateral to the cerebral ischemia.
During a perfusion mode of a perfusion/non-perfusion cycle, the following operations are performed: (1) inflating the left and right pressure cuffs, e.g., to substantially 80 to 100 millimeters of mercury; (2) expanding the member to cover a substantial portion of the cross-sectional area of the superior vena cava causing an increase in cerebral blood flow, retrogradely; and (3) pumping the oxygenated medium from a femoral artery into the catheter for a period, such as a number of (EKG) beats, for example approximately in the range from 2 to 32 or 2 to 100, or any other suitable period. The period may be variable as needed. The catheter may include a second expandable member, e.g., a balloon, circumferentially disposed and sealably attached around a second portion of the catheter substantially adjacent or near the proximal end of the catheter so that the second balloon is positioned near the insertion site. The second balloon is configured to inflate during the perfusion mode to prevent back bleeding from the insertion site. Both or one of the balloons may be self-inflating normal type or a parachute type balloon. During a non-perfusion mode of the perfusion/non-perfusion cycle, the following operations are performed: (1) deflating the left and right pressure cuffs; and (2) collapsing the expanded member. Further operations include coating the catheter with anti-thrombogenic material such as heparin, and using the catheter to measure the central venous pressure in the superior vena cava during both or one of the perfusion and non-perfusion modes. Successive perfusion/non-perfusion cycles may be performed until, for example, a clot in a patient's arterial system is dissolved by thrombolysis, or a ruptured cerebral aneurysm is clipped or endovascularly coiled. The central venous pressure in the superior vena cava may be measured during one or both the perfusion mode and non-perfusion mode.
According to another aspect, a system for providing cerebral protection comprises, according to one embodiment, one or more catheters for selectively perfusing, in various embodiments, the brain through its venous drainage system by SVC occlusion. The catheters can be inserted through an insertion site of either the (right or left) subclavian vein or the (right or left) femoral vein. A combination of both subclavian and femoral veins can be also used. Such systems include a pump, one or more occluding balloons, an EKG monitor and a processor.
A system may optionally include a cooling device to cool the arterial blood, e.g., from a femoral artery, while it is being pumped by a pump into the subclavian vein or the femoral vein. That is, in addition to maintaining and/or improving cerebral perfusion, the method according to one embodiment may combine or otherwise rely on cooling of the cerebral vasculature in treatment of both global and focal cerebral ischemia to inhibit or minimize tissue damage resulting from lack or limitation of cerebral blood circulation. In use, the oxygenated medium that is circulated will be cooled in order to cool the brain tissue and reduce the risk of ischemic damage.